Question: dealing with errors

Hi,

I want (Maple) to do a series of time consuming computations while I sleep so I create a Vector V of length 50 say and make each computation an entry in V.

An occasional entry will turn out to be an error-that is, I get an error message and the calculations stop. Not a serious problem if the first 47 entries have been calculated but if the thrd calcuation fails I have little to show for a night's work.

What I want if for Maple to skip any computaion that fails (produce the appropriate  error message if possible) and then continue with the other computations.  Any suggestions?

Here is an unrelated question. If I have an Array T say
>T:=Array(3..5,7..17,(i,j)->i^2*j):

then T[4,10] returns the appropriate entry. T(2,4) returns the same thing. What type of object is T(-,-)?